Universal Mobile Telecommunications System (UMTS) is a wireless system that is known in the art and is designed to provide higher data rates and enhanced service to subscribers. The Third Generation Partnership Project (3GPP), including the specifications relating to the Evolved Universal Terrestrial Radio Access (UTRA) and Universal Terrestrial Radio Access Network (UTRAN), standardizes UMTS. The UMTS network includes user equipment (UE, also referred to as a “user equipment device” or a “user equipment terminal”), UMTS Terrestrial Radio Access Network (UTRAN), and core network (CN). The UE is interfaced to the UTRAN over a radio Uu interface, while the UTRAN interfaces to the core network over a wired Iu interface. The CN is coupled to an external network, which may include the Internet, a Public Land Mobile Network (PLMN), a Public Switched Telephone Network (PSTN), an Integrated Services Digital Network (ISDN), etc., which can exchange information to and from a UE. A communication terminal (e.g., user equipment) may be a wireless communication terminal such as one employed in a network, not just by an “end user.”
The UTRAN includes multiple Radio Network Subsystems (RNSs), each of which contains at least one Radio Network Controller (RNC). However, it should be noted that the RNC may not be present in the Long Term Evolution (LTE) of UTRAN (E-UTRAN). LTE may include a centralized or decentralized entity for control information. In operation, each RNC may be connected to multiple Node Bs, which are the UMTS counterparts to Global System for Mobile Communications (GSM) base stations. Each Node B may be in radio contact with multiple UEs via the radio Uu interface.
The Third Generation Partnership Project Long Term Evolution (3GPP LTE) project is the name generally used to refer to an ongoing effort across the industry to improve the UMTS for mobile communication to cope with continuing new requirements and the growing base of users. The goals of this broadly based project include improving communication efficiency, lowering costs, improving services, making use of new spectrum opportunities, and achieving better integration with other open standards. The 3GPP LTE project is not by itself a standard-generating effort, but will result in new recommendations for standards for the UMTS.
The wireless communication systems as described herein are applicable to, for instance, 3GPP LTE compatible wireless communication systems and, of interest, are an aspect of LTE referred to as “evolved UMTS Terrestrial Radio Access Network,” or E-UTRAN. In general, E-UTRAN resources are assigned more or less temporarily by the network to one or more UEs by the use of allocation tables, or more generally by the use of a downlink resource assignment channel or physical downlink shared control channel (PDSCCH). The 3GPP LTE compatible wireless communication systems are packet-based systems and, therefore, there may not be a dedicated connection reserved for communication between a UE and the network. Users are generally scheduled on a shared channel every transmission time interval (TTI) by a Node B or an evolved Node B (e-Node B). A Node B or an e-Node B controls the communications between user equipment terminals in a cell served by the Node B or e-Node B. In general, one Node B or e-Node B serves each cell. Resources needed for data transfer are assigned either as one time assignments or in a persistent/semi-static way. The 3GPP LTE compatible wireless communication systems, also referred to as 3.9G, generally support a large number of users per cell with quasi-instantaneous access to radio resources in the active state. It is typically a design requirement that at least 200 users per cell should be supported in the active state for spectrum allocations up to 5 megahertz (MHz), and at least 400 users for a higher spectrum allocation.
In order to facilitate scheduling on the shared channel, the e-Node B transmits an allocation in a downlink-shared channel to the UE. The allocation information may be related to both uplink and downlink channels. The allocation information may include information about which resource blocks in the frequency domain are allocated to the scheduled user(s), the modulation and coding schemes, the size of the transport block, and the like.
A Node B or an e-Node B requires information related to instantaneous channel quality so that it can perform scheduling and allocation. In order for a Node B or e-Node B to be informed of the channel quality, the UE provides channel quality indication (CQI) reports (which may also be generally referred to herein as “channel quality reports”) to the Node B or the e-Node B. The UE periodically or in response to a particular event may “send” (i.e., may “transmit” or may “report”) CQI reports to the respective serving Node B or e-Node B. The CQI reports indicate the recommended transmission format for the next transmission time interval. For an active UE (i.e., a UE that is involved in communication that is configured to use periodic reporting), the UE sends a CQI report every given number of sub-frames. In event-based CQI reporting (i.e., triggered CQI reporting), UEs only send a CQI report when a certain system event has occurred, for instance, when it is assigned a downlink resource or when transmitting an acknowledgement/negative acknowledgement (ACK/NACK) in an uplink. The CQI report may be constructed in such a way that it indicates the expected supported transport block size under certain assumptions, which may include the recommended number of physical resource blocks (PRBs), the supported modulation and coding scheme, the recommended multiple input-multiple output (MIMO) configuration, as well as a possible power offset.
The CQI reports are used for resource scheduling and adaptive modulation and coding. The Node B or e-Node B typically assigns user equipment resources based on their respective channel qualities as indicated by the CQI reports. User equipment is also assigned a code rate and modulation format based on channel quality. The Node B typically attempts to adapt to the current channel conditions of a UE by selecting the highest possible modulation and coding scheme that will keep the frame error probability below a certain threshold, for example 10% in High Speed Downlink Packet Access (HSDPA).
Transmission of a CQI report, like any other transmission from a UE, is an energy-consuming event that detracts from “battery life.” Battery life relates to the battery-recharging interval for the UE, which is a critical market acceptance parameter for an end user.
Considering the requirement for a UE to transmit a CQI report as described above, what is needed in the art for a communication system including UEs powered by an internal battery is a system and method capable of providing CQI reports to a Node B or an e-Node B for downlink packet scheduling and link adaptation to adaptive modulation and coding (AMC) that accommodate conservation of power in the UE, while also providing efficient support of discontinuous reception (DRX) and transmission (DTX) processes operative therein.